Precision gauge



Man". 2Q, 1923.

W. E. HOKE PRECISION GAUGE Filed May 26, 1919 Patented. Mar. 2(0), 11923.

warren stares attains WILLIAM E. HOKE, OF ST. LOUIS,-1llIISSOURI, ASSIGNOJR TO PRATT & WHITNEY COMPANY, OF NEW YORK, N. Y., A COBLOBATION 01E NEW'JERSEY.

rancrsron GAUGE.

Application filed May 26, 1919. Serial No. 299,945.

T 0 all whom it may concern.

Be it known that ll, WILLIAM E. HOKE, a citizen of the United States, residing at St.

Louis, Missouri, have invented certain new and useful Improvements -in Precision Gauges, of which the following is a specification.

The invention relates to gauge blocks having opposite plane parallel surfaces which are sufficiently smooth and plane to enable a series of similar blocks to be wrung together to form a built-up gauge.

The object of the present invention is to provide gauge blocks of this general type having contact surfaces of improved character whereby better and more reliable wringing action can be effected, whereby the blocks are enabled to more effectively resist wear, whereby greater accuracy of engagement is obtained, whereby warping is prevented, and whereby other advantages are secured.

In the accompanying drawing 1 have illustrated a gauge block embodying the invention, but it will be understood that the size and shape of the block may be varied at will, the invention relating to the working surfaces thereof.

Of the drawing: L

Fig. 1 is a plan view of a block embodying the invention, no attempt having been made in this view to illustrate the character of the working surface.

Fig. 2 is a side view of the block shown in .Fig. 1. I

Fig. 3 shows a series of blocks in endwise engagement.

Fig. 4; is a view of a part of the surface of a block as it appears under the microscope enlarged about fifty diameters.

Fig. 5 is a view similar to Fig. 3 but showing the surface of a gauge block such as has been heretofore commonly used.

Fig. 6 is a view of one contact surface of the block as it appears to the unaided eye when held in a certain position as concerns the source of light.

Figs. 7 and 8 are views similar to Fig. 5 but showing-the block with the surface in the same plane but turned to .difierent positions.

Referring particularly to Figs. 1 and 2 of the drawing, it will be seen that I have shown a gauge block A having opposite end surfaces 1 and 2. The block is shown as being square, but this is immaterial as conthe length between the surfaces. In making the blocks use may be made of the method and machine set forth in my copending ap- 'plication for method of and machine for making gauges and other articles, Serial No. 289,591 filed April 12th, 1919.

In using the blocks a series of them, usually of the same transverse size and shape but with different lengths, are placed together in endwise engagement, as indicated in Fig. 3. Ordinarily there isa very thin liquid film between the adjacent surfaces of any two blocks and when the blocks are pressed and wrung together they adhere strongly. ,The lengths of the blocks are either multiples or definite fractions, usually decimal fractions, of a predetermined unit of length. This unit of length may be the inch, or the centimeter or any other convenient unit of length. If the inch is the unit decided upon, the lengths of the blocks are ordinarily multiples of a thousandth of an inch or multiples of a ten-thousandthof an inch. For a given set of blocks with lengths in multiples of thousandths the lengths may be so selected as to make it possible, by combining different blocks in wringing engagement end to end, to construct a built-up gauge having any desired length measured in inches and thousandths. For the combination shown in F ig." 3, the total length is obviously the sum of the .total lengths of the individual blocks A, A A A and A By properly selecting the several blocks any desired total length can be secured."

Obviously the accuracy of a combination such as shown in Fig. 3 is largely dependent upon the uniformity and character of the contact or engagement ofthe several blocks. Absolute contact is not to be expected particularly'when a liquid film is present; but in order to maintain accuracy the degree of separation of the blocks must be as small as possible and must be always the same. The character of the engagement must be uniform, not only between two different pairs of surfaces but also across the entire area of cerns the parallelism thereof, or as concerns any one pair of surfaces so that the end surfaces of the series may be maintained in exact parallelism. In fact, the wringing engagement of 'theblocks must be such that a set of blocks, such as that shown, will always have the same overalljength regardless of any changes in the relative positions of the blocks in the series and regardless of any reversing of the positions of individual blocks.

When two blocks are properly wrung together, the force holding them in engagement is frequently as high as 100 pounds per square inch. The cause and character narily necessary to slide the block surfaces one upon the other in order to secure close engagement and in order to wipe ofl excess liquid and reducethe liquid film to its minimum thickness. In the making of blocks of this character surface scratches varying in I are to be wrung together.

size are almost unavoidably produced.

When properly arranged and distributed these scratches are unobjectionableand are distinctly advantageous if not in fact necessary as they permit the required liquid film to be present between two surfaces which In fact, it has been found under some circumstances that surfaces which are highly polished and substantially without scratches will not wring together. This failure to wring under these conditions may be due to the fact that one smooth surface completely cleans the other,

.there being no scratches to retain minute quantities of liquid.

In accordance with the present invention, each end surface of the block has a large number of minute scratches forming a close net-work of scratches which extend in allv directions. This fact is illustrated in the enlarged Fig. 4, but the showing is imperfeet as the scratches are veryfine and cannot vbe adequately represented by ink lines. The scratches are nearly straight, although they ordinarily conform to arcs of large radii. Inasmuch as the scratches cross each other at every possible angle, there are no superposed parallel scratches. Thus each scratch follows its own individual course.

intersecting other scratches .at various angles. Between the scratches are variously shaped polygonal areas which are substantially free from scratches, or at least free from scratches of the magnitude shown in Fig. 4. These flat areas between the scratches are relatively broad and they unite to form what for practical purposes is a substantially continuous flat surface extending across i the entire block. As already stated, this surface is or may be plane within a millionth of an inch.

As indicated in Figs. 6, 7 and 8, each of the scratches extends completely across the surface of the gauge and is substantially straight throughout its length.

In order that the novel and useful features of my invention may be more readily apparent, I have presented in Fig. 5 a view similar to Fig. 4- but showing the surface of a gauge block of the type which has been heretofore commonly used. It will be seen that this surface consists of a large number of scratches which are parallel or substantially so. Inasmuch as the scratches do not cross each other (except occasionally at very small angles) they are practically superposed, one scratch being frequently located in the bottom of another, thus forming relatively deep grooves. There are no relatively broad unscratched areas, and the working surface consists only of the tops of a large number of the very narrow ridges between the scratches. It will be seen that, when two blocks having surfaces such as'shown in 5;are placed in wringing engagement,

approximate contact at bestoccurs only at the tops ofthe ridges and the total area thereof is necessarily very much less than that of the broad fiat surfaces, as shown in Fig. 4. I

Not only do the scratches on the surface of a block embodying the invention run in all directions, but there are approximately the same number of scratches for each direction, and scratches extending in any given direction are substantially uniformly distributed over the surfaces By holding the block at the proper angle with respect to the source of light, it is possible to plain- 1y see the scratches extending in one direction largely to the exclusion of .the others,- these scratches being approximately uniformly distributed over the surface. By turning the block and keeping the surface in the same plane, other sets of scratches come into view, these other sets being similar to the first and running in the same direction on account of the turning of the, block. This phenomenon will be more clearly understood from an examination of Figs. 6, 7 and .8. These "iews show the block in three different positions with the end surface, however, remaining in the same scratches move with the block but successive sets of'scratches come into view. This peculiar appearance of the block as it is means uniformly distributed over the surface.

, When two blocks having surfaces such as shown in Figs. 4 and 6'to 8 are placed in wringing engagement, as indicated in Fig. 3, the various minute areas between the scratches on the respective surfaces come into approximate contact with each other with a very thin film. of liquid between them. It will be seen that the total area of the film of liquid is or may be relatively large, and

when it is remembered that the several small areas may not vary from a single plane by more than a millionth of an inch, it will .be seen that the thickness of the liquid film can be made exceedingly small and nearly uniform. The large total film area and the small thickness tend to give a large wringing force. With surfaces such as shown in Fig. 5, the liquid film is thin enough to be effective only at the points of approximate contact at the tops of the ridges and therefore the effective film area is relatively small. Furthermore, because of the superposed arrangement of the parallelscratches, some of the ridges are higher than others, thus still' further reducing the area of ap proximate contact and allowing the liquid film to reach its minimum thickness only at occasional points.

Inasmuch as the areas betwen the scratches as shown in Fig. 4, are relatively broad, the block is highly resistant to wear, thus maintaining the desired length after long usage. With the scratches parallel or approximately so, as shown in Fig. 5, the contact is only along the tops of the longnarrow ridges,

' and there is but little metal to resist wear,

with the result that the ridges are soon worn down, thus quickly reducing the efiective length of the block;

It will further be seen that with the construction" as shown in Fig. 4, the scratches of two engage blocks will cross each other at various angles, there being therefore no mal areas of engagement.

possibility of the blocks taking any relative position except that determined by the nor- With the construction shown in Fig. 5, however, if the scratches of one block are parallel with those of the other, there is an opportunity for the ridges of one block to fit into the scratches '-of the other, thus reducing the effective length of the two blocks in combination.

' This fitting together may be very slight, but

when it is remembered that an accuracy of within a millionth of an inch is desired, any source of inaccuracy however small ishighly objectionable. Thus it will be seen that with two given blocks a number of different overall dimensions may be obtained as the In the process of making the blocks the tendency of each scratch made by a grain of emery or other abrasive is to peen or spread the metal adjacent the surface. The tendency of the metal to actually move or spread apart may be largely resisted by the metal underneath forming the main body of the block; but even when no actual movement takes place the surface metal may be placedunder a considerable strain. When the scratches extend in all directions, as shown in Fig. 4, the tendency of those in one direction to spread or peen the metal is largely overcome or compensated for by the scratches running in the various other directions. In the case, however, of the construction shown in Fig. 5, the scratches all run substantially in the same direction and the separating or peening efi'ect is cumulative. The result is, {as may be shownby measurement, that blocks constructed with surfaces as shownin Fig. 5 tend to warp, the surfaces themselves becoming slightly cylindrical.

The reduction of the peening effect in a block embodyin my invention is highly important, particu arly when the block is thin; that is when the length between the two end surfaces is small. With a thin block having surfaces such as shown in Fig. 5, the tendency of the block to warp and for the surfaces to become cylindrical is very great, and it is practically impossible to make a block in which the surfaces are perfectly flat. In accordance with my present invention, the peening efiect of the scratches is largely neutralized by the arrangement of the scratches in all directions, thus enabling me to secure perfectly fiat surfaces.

What I claim is:

1. A gauge block provided with a flat surface adapted to have wringing engagement with a similar surface of another block, said surface having thereon a close net-work of scratches extending in all directions, each scratch, as a rule, being continuous entirely across the surface except as efi'aced in part by other scratches.

2. A. gauge block provided with a flat surface adapted to have wringing engagement with a similar surface of another block, said surface having thereon a close net-work of substantially straight scratches extending in all directions, each scratch, as a rule, being continuous entirely across the surface except as efi'aced in part by other scratches.

egg 1,449,118

3; A gauge block provided with a flat s'urby other scratches, the scratches in any one face adapted to have wringing engagement direction being approximately the same in with a similar surface of another block, said number as those in any other direction and 10 surface having thereon a close net-Work of approximately uniformly distributed. scratches extending in all directions, each In testimony whereof, I hereto aflix my scratch, as a rule, being continuous entirely signature. across the surface except as efi'aced in part WILLIAM E. HOKE. 

